A bipartisan Senate group has agreed on a sweeping legislative proposal that would represent the most ambitious overhaul of the U.S. immigration system in three decades. The Washington Post will be examining portions of the bill on Post Politics in a series of blog entries.

High-tech firms scored a big win in the negotiations over immigration reform, convincing the senators to agree to sharply increasing the number of visas given out each year for high-skilled foreign workers.

The compromise, according to the summary obtained by The Washington Post, would lift the cap from 65,000 to 110,000 – with the number permitted to rise as high as 180,000 in future years.

But several new provisions aim to crack down on big outsourcing firms – many of them based in India – that rely most heavily on so-called H1-B foreign worker visas.

Within three years, for instance, firms that have more than half of their U.S. workers on the visas will be banned from applying for additional visas.

Many other firms would be required to pay their foreign workers more, and face stiffer requirements that they advertise first for American workers before being granted a new visa.

Moreover, many firms employing 50 or more workers, with heavy concentrations of workers with H1-B and L1 visas, would face stiff costs of up to $10,000 per additional foreign worker brought to the United States.

The changes could be a boon for the U.S. tech industry, but could well force big outsourcing companies like Tata Consultancy to revamp their business models.